This invention relates to a polishing device for polishing the main and end surfaces of a semiconductor wafer, a liquid crystal panel, a magnetic disk substrate, an optical fiber connecting part, etc. by means of a polishing tape. More particularly, this invention relates to such a polishing device capable of mechanically carrying out a control of the sequence of polishing steps, the kinds of the polishing tapes and the quality of the produced lots when a polishing process is carried out in a plurality of steps by exchanging polishing tapes.
A thin film is formed over a target object to be polished such as the surface of a semiconductor wafer (as shown in FIG. 10A) but the thin film portions on the beveled portion (B) along the edge of the semiconductor wafer and the edge portion (E) which is a circumferential portion along the inner surface from this beveled potion tend to become a source of particles and other contaminants and hence should be removed. Particles may also be generated from rough areas generated over a beveled portion, depending on the kind of the production process for a semiconductor device such that an improvement in the surface accuracy is coming to be required of portions from which the thin film has been removed.
As disclosed in Japanese Patent Publications Tokkai 2002-208572 and 2003-234314, devices are being developed for removing an unwanted thin film such as a film from portions of a semiconductor wafer surface as described above by using a polishing tape. These devices are adapted to pass a polishing tape from the upper surface to an end surface and then to the lower surface of a semiconductor wafer and to use a polishing head to press the polishing tape onto the semiconductor wafer for removing the unwanted film portions.
When a target object is polished, polishing tapes in several grades including a rough one and a fine finishing tape are alternatingly used for the polishing operation. If an error is committed in exchanging the tapes in this operation, many defective products may end up being produced in the case of an automatic polishing operation. If defective products are mixed in a production lot, it is necessary to quickly detect and remove the defective lot and to investigate the cause of the event. This adversely affects the yield.
A commonly practiced method of distinguishing among polishing tapes of different kinds has been to add different coloring agents into the paints for the polishing tapes but this gives rise to the problem that these coloring agents may turn out to be another source of contamination. It was also a problem that the addition of a coloring agent may adversely affect the polishing characteristic.
Another method of distinguishing among polishing tapes has been to provide a mark on the end surface of the polishing tape or the end surface of the reel core. Since such marks cannot be easily converted into an electrical signal, the distinction must be made visually and judgment errors remained likely to occur. Since the quantity of data is small with such marks, furthermore, it was not possible to carry out the analysis of quality control.